//随机颜色
function randomColor(autoAlpha = true, alpha = 1) {
    var red = parseInt(Math.random() * 255).toString()
    var blue = parseInt(Math.random() * 255).toString()
    var green = parseInt(Math.random() * 255).toString()
    var alpha = alpha
    if (autoAlpha) {
      alpha = Math.random().toString().slice(0.4)
    }
    var color = 'rgba(' + red + ',' + blue + ',' + green + ',' + alpha + ')';
    return color;
  }